Influence of Drying Conditions on Amine-Functionalized SBA-15 as Adsorbent of CO₂

Adsorption of pure CO₂ on amine-functionalized SBA-15 mesoporous silica materials has been studied. Adsorbent materials were prepared by grafting the silica surface with aminopropyl (AP), ethylene-diamine (ED) and diethylene-triamine (DT) organosilane molecules. Materials so obtained were dried under air atmosphere at 110 °C and at room temperature. CO₂ adsorption isotherms were carried out at 45 °C, showing that grafted materials are very efficient for CO₂ removal at atmospheric pressure when samples are dried at 20 º C. However, when the drying step is carried out at 110 °C in air, CO₂ adsorption capacity is low. DRIFTS analysis has shown that amino groups can undergo oxidation to oxime or imine species during drying. Adsorption capacity of the materials was found to be unchanged after some consecutive adsorption–desorption cycles, being the regeneration step performed at 110 °C under vacuum.